>
> > modified PK232 to see how good it is. I already know that my
> modified 232,
> > which is superior to a stock 232,
>
> What kind of RTTY MODS are there for the PK-232 and where might I
> find them?
I wrote an article for the now-defunct "Communications Quarterly" in 1993,
and then did some additional work. The mods scale down the bandwidth of the
front end bandpass filter by almost a factor of 2 (user-selectable), and the
post-detection LPF by about 5, without affecting VHF packet performance.
Aftermarket DSP boxes can now substitute for the front-end scaling (only). I
also double the Q of the discriminator resonators, which changes the
transfer characteristic from the classic "S-curve", which is best for the
300 bps modes, to a double-humped response more suited to the spectrum of an
FSK signal.
The mods involve replacing a handful of 1% resistors and going through a
tuning procedure on the front-end BPF that requires a dual-channel scope or
other phase-comparison device.
Over the years, I have sent copies of the article and subsequent additions
to many requestors, at least one of whom may actually have done the mods.
:-) I have several requests in the hopper and I would be happy to send
copies to anyone willing to send me an SAE and $2 to cover copying a dozen
pages and mailing a 3 ounce letter.
>
> > You say your KAM "actually keys true FSK," but that is not correct. The
> KAM,
> > and all other "FSK" sources, provide logic-level outputs that do not
> > directly manipulate the frequency generator in your radio, but which
> select
> > dividers in the radio that provide tones to modulate your SSB
> transmitter
> > downstream from your microphone preamps. IOW, you are merely generating
> AFSK
>
> I don't know about the KAM, but the PK-232 provides a discrete output for
> FSK. When used with a TT OMNI-VI+, this voltage is applied to
> the VFO and a
> varactor diode shifts the VFO frequency, providing true FSK.
>
> Jim
>
That is indeed true FSK, and that is the first modern radio I have heard of
that does that. So, if Ford, N0FP has an Omni VI, his claim of bypassing all
audio circuitry was correct. Thank you for that input and correction--I had
hoped that my statement would bring forth that information. I wonder if
other Tentec radios do the same.
Garry, NI6T
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